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Sunday, December 7, 2014

The Second Law in Classical vs. Chemical vs. Feinmaniacal Thermodynamics

I had written the bulk of my last post of similar title, The Second Law in Classical vs. Chemical Thermodynamics, a while ago, and wasn't sure whether to do my usual tidying up (sorry, that generally doesn't include editing for word count!) and hit publish, because it seemed a bit tangential.



That heading links to a public Facebook post by Richard "Entropy & Mirrors" Feinman  [even if you're not on FB you should be able to read it, however just in case, I printed to PDF and uploaded to my online drive].  

Before I go on, here is a short video by Feinman from which I've derived his new nickname of Entropy & Mirrors.  If you refer back to my prior post, it should start to become clear just how confusing Feinman's interpretation is here.  

I think that Feinman likes to weave his "relationship" to Richard Feynman in whenever he can.  He even posts to feinmantheother.com ... as if having the same sounding name (not even the same name!) conveys the stature of one upon the other.   But I digress ...
The point of running a video backwards is to put common sense in complex concepts, but sometimes these exercises backfire.  I saw first saw this video around the time I was reading Haynie's Biological Thermodynamics book and lo and behold, Haynie used the smoke analogy as well:
The direction of spontaneous change in an isothermal system from a non-equilibrium to an equilibrium state is determined by the requirement that the extent of change be a maximum at every point on the reaction pathway. The suggestion that, say, uniformly dispersed smoke particles could somehow move spontaneously from all corners of a room back into a burning cigar seems absurd – except in a videotape run backwards.
The "playing backwards" idea relates to the seeming disconnect between the laws of physics -- which are time agnostic -- and the unidirectional nature of time (it's always moving forward).  Also, intuitively we know that the smoke from the cigar (or the engine) cannot be put back together again and uncombusted.  This is discussed in greater detail in Brian Greene's Fabric of the Cosmos, the most relevant Chapter 6 is available here (free).  What might be an interesting thought process to consider  is boiling water in a pot with a lid.  The steam that comes from the boiling water (increasing entropy in liquid → gas) is easily "put back together again" on the lid to reform liquid water.  If you were to record a glass kettle of boiling water, then watch that in reverse, the only indicator of time would be the direction of the air bubbles in the boiling water and the water droplets condensing back in.  There's nothing strange about vapor returning to water though.

So here again I turn to Wikipedia for a summary:

And there at the end of the paragraph you have the kicker.  On a regular basis, the First Law is erroneously dismissed on the basis of the human body being an open system -- and yet, that is the whole point of "Calories In - Calories Out" and the real utility of the "black box" in analyzing open systems.    And yet, the Second Law is specifically limited to isolated systems -- no inputs or exchanges.  This +ΔS is NOT what individually drives chemical reactions (though it can) in any system (open, closed or isolated), and it is NOT a requirement of the reaction to occur or be considered irreversible from a practical standpoint (see my last post, combustion of methane has a slight -ΔS)



Blame the Revolution!

So anyway, on Facebook, Feinman made a similar point as in my last post, regarding the context in which one has been introduced to the concepts of thermodynamics:
Here's how it plays out: thermodynamics comes from the industrial revolution where it was important to see how efficient you could make a heat engine. Mathematically, you wanted to know, if you added an amount of heat, q, to the machine, how much work, -w, could you get out; the minus sign means that the work is done by the system (the machine), that is, put in heat, get out work. (Mathematically, any heat given off by the machine would be -q).

The amount of work per unit heat is roughly the efficiency of the machine. Both q and w are variable, depend on different conditions but isn't there something that will tell us about the absolute ability of the machine to do work? The first law says that there is a thing, called the internal energy, usually written U, that is conserved. It's not something you can really measure but if it changes, the change in U, written ΔU is equal to the sum of heat added minus work done. First law: ΔU= q-w.
This much is good. And yet, to borrow a phrase from Gary Taubes, it tells us nothing :-)  Or maybe it does, but it's irrelevant to the human being because we are not steam engine locomotives, but rather electrochemically powered bipeds.   Feinman gets himself in trouble in the next sentence:
That's the first law of thermodynamics. The subtleties of thermodynamics, however, tell you why people mis-apply it in CICO. The energy that is conserved, U, describes the state of the system. It is said to be a state variable and it doesn't matter how you got there.
Nonsense!  That  Δ there means "change in", not energy conserved. As in 

ΔU=CI-CO

This the First Law as applied to a "black box" scenario.  In the engine the input is q and the output is w.  Therefore the energy of the system will change if qin ≠ wout.   How does that not apply then to a human (or any other) black box?   Answer:  It does apply!  ΔE = Ein - Eout.    Come on already!!!   The First Law is about conservation of all the energy in the universe.  When applying it to closed or open systems -- both of which can exchange energy with the surroundings -- it is all about the change in the energy of the system.   STOP CONFUSING PEOPLE on this simple concept.  CICO is ΔE = CI - CO, not CI=CO.  It is not about conservation in the human, it is about changes in energy stores.   

To further confuse matters, in the previous paragraph, Feinman reiterates:  
The bottom line is that the real force of thermodynamics is not in the first law which is a conservation law but in the second law which is a dissipation law. Things are not conserved, they are lost. That is why thermodynamics is considered the first revolutionary science.
Excuse me if I again point out that he is stating that the First Law is wrong!  Energy is not lost, even in the steam engine which just has some residual heat that couldn't be converted back to useful mechanical work.   In the real world application, this heat dissipates into the environment, it is lost to the system, but that is not the same as disappearing!!  

Remember the video from my last post?  That reaction between two solids (barium hydroxide and ammonium chloride) was endothermic, meaning the products contain more chemical potential energy compared with the reactants.  This would not occur spontaneously were it not for the highly favorable entropy change.  However when it did, the reaction system "sucked up" heat from the surroundings, in this case including water between the wooden block and the beaker, thereby freezing the water.    For all intents and purposes, a Second Law driven reaction where energy was gained by the system.  Tell me again about dissipation and how this what makes the world go round!

In chemistry and chemical physics, it is important to reiterate that heat is energy, and that physicochemical energy is related to heat.   This is why we talk about the heat of formation, the heat of fusion, the heat of vaporization, the heat of solution, and why bond energies are denoted by "H".   In a way, chemical potential energy could just as well be thought of as the storage form of heat, with heat transfer being the kinetic form.  The concept of entropy may explain the "flow" of heat from hot to cold, and the effect of entropy may be temperature dependent, but heat is heat is energy.  In the above example the ΔH term is heat gained, not lost.  

Furthermore, it is vexing how Feinman can continue to repeat this dissipation argument in the context where he recognizes that many of the reactions in our bodies are synthesis reactions -- e.g. building, decreasing entropy, etc. -- the net result of which are highly endothermic processes.  Feinman continues: 
(1) Another way of stating the second law is that all real processes are inefficient, that is, (2) looking at metabolism, there is a limit to how much you can get out of the oxidation of food in terms of making cell material and doing manual labor.   (3) Some of the energy in the oxidation must be lost for heat, (4) random reallocation of metabolites, (5) futile cycles and (6) conversion of low entropy compounds, like protein to high entropy compounds like fat.  (7) It is not excluded that all metabolic processing of food has the same efficiency but the likelihood is infinitesimal.
Say WHAT?  Let's take these using the blue numbers I used to break up the paragraph. 

(1) ... all real processes are inefficient:  The concept of efficiency is another one that is just used to confuse people.  (Aside:  the low carb advocates seem unable to agree on whether inefficiency or efficiency is the goal anyway!).  A combustion (burning of fuel) reaction would be less efficient in an engine where only mechanical work "out" is useful, but take the same reaction and use it to heat water, and voila!  Heat = useful = instant efficiency! I've been making this point regarding human (warm blooded) beings for a while now as well.  If one measures efficiency only as net ATP formed, it is low (around 40%).  Heat given off in this process, however, is not waste to in an organism that must maintain body temperature or it will die.  

(2) ... there is a limit to how much you can get out of the oxidation of food in terms of making cell material and doing manual labor:  Yes, there is a limit to how much energy you can get out of your food, and there is a limit to how much of that goes to do chemical work.  Those limits are "hardwired" into the metabolic pathways, however.  Most of these reactions are in common pathways anyway, so this fuss over heat vs. ATP and energy distribution gets pretty ridiculous on its face after a while.

(3) Some of the energy in the oxidation must be lost for heat:  For every 10J released in a hypothetical reaction, the biochemistry dictates that 6J is absorbed by another reaction and 4J given off as heat.  Or 9J + 1J ... or 1J + 9J.  This same distribution occurs each time, and regardless of where the reactants came from.  In yet another way heat production can be considered fruitful, it is the highly exothermic reactions in the Krebs cycle that keep it turning, despite the neutral energetics of some steps, and even the markedly unfavorable energetics of the malate to oxaloacetate reaction.

(4) ... random reallocation of metabolites:  Say WHAT???  There is little that is random in biochemistry!  Certainly not the reallocation of metabolites whatever the heck that is supposed to mean.

(5) ... futile cycles:  The use of so-called futile cycles by the body is not a thermodynamic issue with the exception that they are used to deliberately produce heat (in which case the term "futile" is a bit of a misnomer as it implies no purpose or desired outcome) or dissipate energy excesses.  Both of these increase calorie expenditure and have nothing to do with the energy supplied by various food molecules.

(6) ... conversion of low entropy compounds, like protein to high entropy compounds like fat:  This is a new one!  I would like to think that Feinman merely misspoke here ... but there is nothing about different macros that makes them "high" or "low" entropy.  Any such designation would be "compared to what" and there's certainly no broad generalization for protein (which could be small peptides or macromolecules like collagen) versus fat (at quite a range of chain lengths!).  The LCFA is "low entropy" compared to the acetyl groups that make it up.  The laws of thermodynamics only dictate how much energy must be provided for the reaction to occur.   If Feinman is referring to energy requiring synthesis reactions, they are irrelevant to the discussion of whether heat or ATP is the ultimate product of metabolic catabolism.  That energy is to be accounted for in "calories out" and those processes are most certainly not dissipation!

(7) It is not excluded that all metabolic processing of food has the same efficiency but the likelihood is infinitesimal:  This has nothing to do with Second Law dissipation.  And again, whatever the energetics are at the biochemical level, most are in shared pathways.   The next and last line of that paragraph was:

Some metabolism of food gives you more productive effects than others. If you think the differences are small then you don't have to act on it but you might want to attend to the work of people who are trying to maximize the effect. It certainly makes sense to see the mechanisms by which it can be done.
Attending to the work of people trying to maximize something that doesn't exist?  The low carbers have been claiming this mythical metabolic advantage stuff for a very long time.  For over a decade now, Feinman has been postulating about how this might be exploited for fat loss.  You'd think they'd have some actual evidence by now.  Oh wait ... NuSI!  Nope, they are soon to be spending $14 million to use calorie restriction to reduce overweight people by 12% body weight.  If they aren't attending to the gimmickry of Eades, Bailor and Kiefer, why is Feinman encouraging you to??


But wait! There's more!!

In his last paragraph, Feinman says something I haven't seen him say before:
The heat generated in a chemical reaction depends on how you do the reaction. 

What?  Here I really hope he misspoke!!  But I don't think so, because he's previously made many erroneous statements in far more formal venues, such as the abominable First Law Violates the Second Law paper.   I do believe my understanding of what Feinman is saying has improved from reading his Facebook postings, such as the one that inspired my post on the calories in a gallon of gas.  He is confusing the energy consumed by other reactions in the body with that produced from the breakdown of food molecules.   Ultimately, 
carbohydrate + oxygen → carbon dioxide + water + HEAT
fatty acid + oxygen → carbon dioxide + water + HEAT
amino acid + oxygen → carbon dioxide + water + ammonia + HEAT
Each CO2 molecule that you exhale came, at some point, from a carb, fat, or protein molecule that you have consumed (except for what you may have inhaled, just to be thorough).   That carbon, in that molecule can be "attached" to a specific NET amount of heat released from it's "liberation" from its molecular bonds.  This energy is "Calories In".  This is energy added to the system that is your body.  The fate of the energy released does not change this.  Let me repeat for the ketos (ht JF ;-) ) in the audience:  The fate of the energy released does not alter the caloric content of your food.  

In chemistry, all of the following are state functions:  G (free energy), H (enthalpy, heat), and S (entropy).   These quantities describe the state of a system that are independent of the path that got you there.  Hess's Law is based on this principle:

Hess's law of constant heat summation, also known as Hess's law (or Hess' law), is a relationship in physical chemistry named after Germain Hess ... [it] states that the total enthalpy change during the complete course of a chemical reaction is the same whether the reaction is made in one step or in several steps.
Hess's law is now understood as an expression of the principle of conservation of energy, also expressed in the first law of thermodynamics, and the fact that the enthalpy of a chemical process is independent of the path taken from the initial to the final state (i.e. enthalpy is a state function). It applies to the special case of paths consisting of chemical reactions (or changes of state) at constant temperature and pressure.
Just in case anyone thinks to challenge the relationship between enthalpy and heat, Feinman gets this part right in his video.  

Hess's Law is the direct opposite of Feinman's Scofflaw (the literal translation of which -- "a compound of the words scoff and law, meaning one who mocks or ridicules the law" -- fits well here).   As Donald Haynie wrote:

So, whether you do
C6H12O6 + O2 6CO2 + 6H2
in a calorimeter, or
Glucose C6H12O6 → Glucose-6-phosphate → Fructose-6-phosphate → Fructose-1,6-bisphosphate → Dihydroxyacetone phosphate (to Glyceraldehyde-3-phosphate) + Glyceraldehyde-3-phosphate → 2(Glyceraldehyde-3-phosphate) → 2(1,3-Bisphosphoglycerate) → 2(3-phosphoglycerate) →  2(2-Phosphoglycerate)→ 2(Phosphoenolpyruvate) → 2(Pyruvate) → 2(Acetyl-CoA) + 2(CO2) ... 2(Acetyl-CoA + Oxaloacetate) → 2(Citrate)  → 2(Isocitrate) → 2(Alpha-Ketoglutarate) + 2(CO2) ...  2(Alpha-Ketoglutarate) → 2(Succinyl-CoA) + 2(CO2) ... 
in your body, the end result is the same.  By the succinyl-CoA step in Krebs, you've gotten all of your "Calories In" and what has been released into your body as heat or what is tied up in ATP, or in reducing equivalents bound for the electron transport chain, is dictated by the biochemistry.  The process becomes no more or less efficient in terms of the energy obtained from the glucose.  And that's really the bottom line.


Everything else ... everything ... is "Calories Out"

Every other chemical reaction -- including, or shall we say especially, those to which oxidation reactions are coupled --  "Calories Out".   

  • That ATP to phosphorylate the glucose?  It's using internal energy to do chemical work.  Calories Out.
  • That ATP phosphorylating the head of a myosin filament?  Doing chemical work to perform mechanical work.  Calories Out.  
  • Substrate cycling (e.g. glycogen synthesis and breakdown) ... Calories Out.  
  • Brown fat uncoupling for thermogenesis?  Calories Out.
  • Futile cycling to generate heat?  Calories Out.
  • Increased metabolic rate?  Increased Calories Out.
  • Decreased metabolic rate?  Decreased Calories Out.

Feinman Should Not Be Teaching Thermodynamics:

I am writing a paper for education journal ... The article that I am writing (in which I emphasize that, in thermo, it is sometimes hard to see the big picture) I point out that in teaching the first law, students can already see that calories in-calories out is not sensible.
What is there left to say at this point other than this man is confused and ought not to be spreading his confusion to others in the name of advocacy for his low carbohydrate gimmickry.    If you don't believe me, see the Haynie quote -- Haynie's being the book most often cited to seemingly refute the truth that people like myself are saying.
In metabolism, work can be generalized to chemical work, making DNA, making protein, etc. and the relative heat and work (generalized here) is very much process-dependent so whereas the total energy change ΔU is conserved, the relative productive vs. non-productive changes is dependent on conditions, they only have to add up together to conserved energy.  Individually they are not conserved. So, why are people still arguing about this?  Don't know.

I hope this helps.
I think this helps elucidate his errors in logic and/or comprehension. 


7 comments:

Kitty said...

Wow. This all seems to me like arguing about how many angels can dance on the head of a pin.


I have noticed that the argument has moved from "eat an unlimited amount of the right kind of calories and you can be lean" to "I'd be this fat even if I ate nothing but carrots - in point of fact, I'd be fatter." It kind of had to.

Sanjeev Sharma said...

> The heat generated in a chemical reaction depends on how you do the reaction

This VERY superficially reminds me of Chem / Mech engineering analysis of thermodynamic cycles for combustion, where running the cycle(or parts of it) at different temperatures gets more or less usable work ... can't wait for them to discover and manipulate this body of work ...

and mis-appropriating this corpus, ignoring that this either

1 is always completely within the framework of conservation laws ... it's always about increasing efficiency; there's NEVER the imputation that one law "trumps" the other or there's any way to "cheat the system".

or 2 applies to the entire thermodynamic cycle for combustion, not the energy ONE reaction produces.

Sanjeev Sharma said...

yes, moving away from ideas that might possibly be falsified to rationalizations that are less so.

other parts of that community are sinking deeper into the various pathologies of bad science, bordering on delusion ... exemplar one: The Hahn / Petro "expanation" for the potato diet's effectiveness.

MacSmiley said...

Can you explain Hahn/Petro in a nutshell?

MacSmiley said...

It is that NUTshell?

Sanjeev Sharma said...

I started typing up my old understanding and thought I should check my memory and whether Petro's supported his ideas better.

I canNOT figure out what I thought I understood; it's a confused MESS.

I don't want to give him hits but I think it's linked here:

http://carbsanity.blogspot.ca/2011/03/insulin-caused-cerebral-stress.html

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